In particular, polyanilines, which are included in various electrically conductive polymers, have good stability in air, and their applications are considered in various fields. Typical examples of their applications may include cathodes of secondary cells, solid electrolyte capacitors, antistatic materials, transparent electrically conductive films, and electromagnetic wave shielding materials.
In most of these applications, polyanilines are used for coating various materials. In this case, properties required for coated films may include, in addition to conductivity which is the property derived from the polyaniline component, film-forming properties, strength, and flexibility as coated films.
However, in general, polyanilines don't have enough solubility nor dispersibility in water or a hydrophilic solvent, so that when used as a coating composition, it is possible to give only a coating composition containing a small amount of the polyaniline component. Therefore, the coated films formed from such a coating composition have insufficient conductivity, or when the polyaniline component is dispersed forcibly, the resultant coated films have problems such as deteriorated film-forming properties as uniform coated films and insufficient strength and flexibility of the coated films themselves because the state of dispersion is deteriorated.
To solve these problems, there have been proposed a method for obtaining a polyaniline-containing composition having excellent dispersibility by carrying out the oxidative polymerization of an aniline monomer in the presence of an emulsion polymer, and a method of mixing a doped polyaniline component and an emulsion polymer (e.g., see Japanese Patent Laid-open (Kokai) Publications Nos. Shou 64-69621 and No. 2000-256617).
However, in the above methods, the oxidative polymerization of an aniline monomer in the presence of an emulsion polymer is very slow, and it is possible to give only polyanilines having a low molecular weight. Therefore, there are problems that the resultant coated films may have insufficient conductivity and that the coated films formed from the polyaniline-containing composition may have lowered water resistance because a large amount of dopant is required for preparing doped polyanilines which can form a stable mixture with an emulsion polymer.